San Francisco voters will decide in November if developers in certain downtown neighborhoods will be required to give more to the arts with Proposition X.

The measure only impacts developments in the Mission and parts of South of Market.

Prop. X, also called Preserving Space for Neighborhood Arts, Small Businesses and Community Services in Certain Neighborhoods, will require developers to replace arts, community and light industrial and repairs operations that their projects impact.

Specifically, the measure would require replacement of any light industrial operations that use 5,000 square feet or more; community uses, such as day care, of 2,500 square feet or more; or arts activities of any size.

Exceptions to the measure are projects approved before June 14, 2016; and projects that offer 100 percent affordable housing units.

As it stands each development in the area is required to follow planning codes and zoning in an area city planners had rezoned in recent years to encourage growth. Still, many projects that fall outside of zoning rules — for bulk, height and use — can apply for conditional use permits.

Proponents of Prop. X say the measure is required to prevent developers from eliminating such properties from an area.

“Unless we pass Prop. X, we face an irreversible loss of affordable spaces for neighborhoods arts, small blue-collar businesses and community services that make up our city’s cultural heritage and local economy,” reads a statement by the measure’s proponents, which include supervisors Jane Kim, Aaron Peskin, David Campos and Norman Yee.

Opponents, who include SPUR’s Executive Director Gabriel Metcalf and SFMade’s head Kate Sofis, say that while the up-zoning of the area is in need of assessment, the measure is not the solution.

“After more than 10 years of public debate, the Board of Supervisors passed zoning rules for the Eastern Neighborhoods that strike a balance between keeping space for industry, artists and nonprofits and housing,” reads the opponent’s statement on the ballot measure.

“We agree that it is time to assess whether the balance is right — and to make changes if it isn’t. But this measure, hastily conceived, with no analysis or data, and no outreach to affected neighborhoods, is not the way to do it.”